CVE-2020-3164: Cisco Cloud Email Security

Medium severity, CVSS 5.3. EPSS: 1.3% chance of exploitation in the next 30 days.

A vulnerability in the web-based management interface of Cisco AsyncOS for Cisco Email Security Appliance (ESA), Cisco Web Security Appliance (WSA), and Cisco Content Security Management Appliance (SMA) could allow an unauthenticated remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to improper validation of specific HTTP request headers. An attacker could exploit this vulnerability by sending a malformed HTTP request to an affected device. A successful exploit could allow the attacker to trigger a prolonged status of high CPU utilization relative to the GUI process(es). Upon successful exploitation of this vulnerability, an affected device will still be operative, but its response time and overall performance may be degraded.

Affected products

• Cisco Cloud Email Security: up to and including 13.0.0-392
• Cisco Content Security Management Appliance: before 13.6.0 (fixed in 13.6.0)
• Cisco Email Security Appliance: up to and including 13.0.0-392
• Cisco Web Security Appliance: up to and including 12.0.1-268

Published 2020-03-04. Last modified 2026-06-17.